Wednesday, March 10, 2010

Becoming Cyborgs--One Organ At A Time

One of the most important steps in becoming a cyborg is developing a stable, working interface between electronic devices and nerve tissue. Nanotechnology has produced the nanotube, which not only serves as a scaffolding for the re-growth of damaged nerve tissue--nanotubes can also serve as interfaces between electronic chips and nerves.

Writing today in Advanced Materials, Nicholas Kotov of the University of Michigan and colleagues describe how they have used hollow, submicroscopic strands of carbon, carbon nanotubes, to connect an integrated circuit to nerve cells. The new technology offers the possibility of building an interface between biology and electronics.

Kotov and colleagues at Oklahoma State University and the University of Texas Medical Branch have explored the properties of single-walled nanotubes (SWNTs) with a view to developing these materials as biologically compatible components of medical devices, sensors, and prosthetics. SWNTs are formed from carbon atoms by various techniques including deposition and resemble a rolled up sheet of chicken wire, but on a tiny scale. They are usually just a few nanometers across and up to several micrometers in length.

The researchers built up layers of their SWNTs to produce a film that is electrically conducting even at a thickness of just a few nanometers. They next grew neuron precursor cells on this film. These precursor cells successfully differentiated into highly branched neurons.

A voltage could then be applied, lateral to the SWNT film layer, and a so-called whole cell patch clamp used to measure any electrical effect on the nerve cells. When a lateral voltage is applied, a relatively large current is carried along the surface but only a very small current, in the region of billionths of an amp, is passed across the film to the nerve cells. The net effect is a kind of reverse amplification of the applied voltage that stimulates the nerve cells without damaging them.

High quality, low cost single-wall (SWCNT) & multi-walled (MWCNTs)Kotov and his colleagues report that such devices might find use in pain management, for instance, where nerve cells involved in the pain response might be controlled by reducing the activity of those cells. An analogous device might be used conversely to stimulate failed motor neurons, nerve cells that control muscle contraction. The researchers also suggest that stimulation could be applied to heart muscle cells to stimulate the heart.

In addition to neural-electronic interfaces, good cyborgs should also have a good supply of artificial organs, such as kidneys. Cyborgs, like conventional humans, may be injured, and will need replacement parts.

To make bioartificial kidneys, scientists grow cells harvested from donor kidneys not suitable for transplant and then insert them into a specially developed filter tube. Because the finished product contains live cells, it is treated like an organ for transplant, flown to the receiving hospital by helicopter in a temperature-controlled case. Humes founded a company, now known as RenaMed, to commercialize the device, which has not yet been approved by the Food and Drug Administration.

Early clinical trials of the device show that it can dramatically improve the health of patients with acute renal failure. According to the results of a trial released last year, patients treated with the device showed a 70 percent improved survival rate 28 days after treatment. (Scientists at RenaMed are currently analyzing interim results from a subsequent trial.)

However, the devices used in these trials were made with a manufacturing process that is only appropriate for growing small batches of cells. To run the larger clinical trials required for approval by the FDA and to supply needy patients if the device is approved, RenaMed will need to find a way to make and deliver the device on a much larger scale.

Humans evolved over billions of years. Now that human medicine influences human evolution, humans may be close to a dead end of sorts. Cyborgs--part human, part machine--will be one way out of the rut in the short term. Genetic engineering of germ tissue will be another way humans will jump-start evolution. A combination of both approaches is most likely in the intermediate term.